Pollen morphology of Boraginaceae s.l. from Brazilian forest fragments: aperture types and ornamentation on Cordiaceae and Heliotropiaceae

Abstract

Boraginaceae s.l., the single family of Boraginales, are extremely diverse in terms of morphology, their species are well distributed in South America especially in Brazilian ecosystems. The pollen morphology of 11 Brazilian native species and four genera (Cordia L., Varronia P. Browne, Heliotropium L. and Myriopus Small) of Boraginaceae s.l. was investigated in order to expand the morphological knowledge of their species, contributing with new data for the palynology, taxonomy, and conservation of the family. The pollen grains were acetolyzed, measured, photographed using light microscopy (LM) and scanning electron microscopy (SEM), and described qualitatively. The analyzed species present differences in size, shape, type and number of apertures (3-porate, 3-colpate, 3-colporate and heterocolpate) and exine ornamentation (psilate, echinate, microechinate-verrucate, reticulate and rugulate) of the pollen grains, allowing the distinction of species studied. Multivariate analysis of measurements confirms the qualitative description and pollen diversity in Cordiaceae species. Smaller diameter values and similarities in aperture and exine ornamentation characterize the Heliotropiaceae species.Our data reinforce the taxonomic importance of pollen morphology and Boraginaceae s.l. as eurypalynous.